我是 Facebook + 原生 Android 的新手。我乖乖地按照他们网站上的步骤操作，但即使我使用 Facebook 成功登录，我仍然会在 session.isOpened() 方法中收到“错误”结果。我相信我已经正确设置了哈希键、包名和类名。你能帮我看看这段代码有什么问题吗？
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// start Facebook Login
Session.openActiveSession(this, true, new Session.StatusCallback() {
// callback when session changes state
@Override
public void call(Session session, SessionState state, Exception exception) {
if (session.isOpened()) {
// make request to the /me API
Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {
// callback after Graph API response with user object
@Override
public void onCompleted(GraphUser user, Response response) {
if (user != null) {
TextView welcome = (TextView) findViewById(R.id.welcome);
welcome.setText("Hello " + user.getName() + "!");
}
}
});
}
}
});
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
Session.getActiveSession().onActivityResult(this, requestCode, resultCode, data);
}